Since the birth of the micromirror device, many kinds of micromirrors have been developed and used for various kinds of optical applications. Most of them have one degree of freedom rotation without any out-of-plane motion, that is, only tilt about one axis. For more complicated optical applications, gimbal structured micromirrors have been developed to have rotational motion about two axes. However, those kinds of micromirrors with gimbal structure have exposed structures to support and to rotate micromirror structure. Since such structures are big in size and the control structures are not concealed, the optical efficiency of the micromirror is decreased due to the low fill factor of the device. Also big out-of-plane dimension and high power consumption are major problems of gimbal structured micromirrors.
Smaller sized micromirror makes the out-of-plane motion amounts reduced and also improves the efficiency of the micromirror motion. There are few micromirror structures to improve optical efficiency and motion efficiency with multi-axis rotation and translation such as U.S. Pat. Nos. 6,028,689 to Michalicek, No. 6,906,848 to Aubuchon. Those structures are using appropriate flexure structure and concealed underneath structure.
After the concealed structure is developed, the size and motion efficiency problems seem to be solved since they offer a good fill factor of the system and motion efficiency. But there still remains bunch of problems to be solved to have efficient motion and higher optical efficiency, such as weaknesses in structural stability, structural flexibility, motion controllability, and so on.
To overcome the disadvantages of the prior arts, the present invention discloses new structures and designs for the micromirror with multi-axis rotation and translation with structural stability and controllability.
Especially the micromirror structure of the present invention has a lot of advantages such as high controllability of the micromirror system, structural stability thanks to the newly introduced top electrode plates, and high efficiency of the micromirror motion.